In order to obtain users’ massive innovative resources and real user needs, enterprises open product innovative design process to users. Due to the involvement of a large number of unorganized and autonomous individuals, the dynamic and complex evolution of the design process has gradually attracted attention. Unlike the existing literature, which regarded the user’s proposed product solution as a constant, the process of user participation in design was regarded as a dynamic gradient process. Therefore, the user’s individual solution and the product model interacted and iterated in the process. Firstly, the typical results of individual interaction of the user were studied. Based on the game theory, the game model was established and its Nash equilibrium was solved. Secondly, the dynamic evolution of user groups was analyzed and its growth process was simulated. The simulation results were compared with the definition of the scalefree network, and the conclusion was drawn that the user group involved in the design was a typical scalefree network. According to the user’s individual interaction model and the user group network model, the software simulation was carried out. The coal crusher design project was used as a case study to verify the correctness of the theoretical model and simulation results. The conclusion that the product model tended to converge in different communication environments was obtained. This conclusion provided a theoretical basis for the application of a large number of users to participate in the design. According to the discrete point simulation and the surface fit, the convergence speed distribution of product solution with user’s game income as the argument was obtained. It was concluded that the convergence speed of the overall solution of the product was related to the parameters of the interactive environment, which was more complex and irregular. Therefore, dynamic monitoring was important when users were involved in the product design process.